Yes boys and girls can be just friends. It happens quite often.
No boy is "attracted" to (every) girl and vice versa. There are also gay and lesbian people who have friends of the opposite sex as well.
Naturally there are some boys and girls who "settle" for friendship if it means they get to spend time with the person they're attracted to. There are also some people who actually believe in the "lets be friends first" philosophy before getting involved.
Generally speaking there are two challenges with boy and girl friendships.
1. It's not uncommon for one of them to secretly desire more than friendship. They complain about being stuck in the "Friend Zone".
2, Another issue is when one or both (friends) have significant others and their mates may insist they stop hanging out with their "friends".
Given a choice between being with someone they're "in love" with or hanging out with a "platonic friend", someone they view as a sister or brother...etc Most people will (choose love) over their friend if it will keep the peace in their relationship.